java连接数据库的代码

1.连接MySQL数据库

package mysql;

import java.sql.*;

/**
 * @author xys
 */
public class ConnectMysql {
    public static Connection getConnection() throws ClassNotFoundException, SQLException {
        String url = "jdbc:mysql://localhost:3306/databaseName";
        String user = "mysqluser";
        String password = "password";
        String driverClass = "com.mysql.cj.jdbc.Driver";
        Connection connection = null;
        Class.forName(driverClass);
        try {
            connection = DriverManager.getConnection(url, user, password);
        } catch (SQLException e) {
            e.printStackTrace();
        }
        if (connection != null) {
            System.out.println("数据库连接成功");
        } else {
            System.out.println("数据库连接失败");
            connection.close();
        }
        return connection;
    }

    public void getResult() throws ClassNotFoundException, SQLException {
        // 实例化 Statement 对象
        Statement statement = getConnection().createStatement();
        // 要执行的 Mysql 数据库操作语句（增、删、改、查）
        String sql = "";
        // 展开结果集数据库
        ResultSet resultSet = statement.executeQuery(sql);
        while (resultSet.next()) {
            // 通过字段检索
            int id = resultSet.getInt("id");
            String name = resultSet.getString("name");

            // 输出数据
            System.out.println("ID : " +id);
            System.out.println("name :" + name);
        }
        // 完成后需要依次关闭
        resultSet.close();
        statement.close();
        getConnection().close();
    }
}

2.连接Oracle数据库

package cn.zhisheng.test.jdbc;

import oracle.jdbc.driver.OracleDriver;
import java.sql.*;
import java.util.Properties;
/**
 * Created by 10412 on 2016/12/27.
 * JDBC的六大步骤
 * JAVA连接Oracle的三种方式
 */
public class JdbcTest
{
    public static void main(String[] args) {
        Connection connect = null;
        Statement statement = null;
        ResultSet resultSet = null;

        try {
            //第一步：注册驱动
            //第一种方式：类加载(常用)
            //Class.forName("oracle.jdbc.OracleDriver");

            //第二种方式：利用Driver对象
            Driver driver = new OracleDriver();
            DriverManager.deregisterDriver(driver);


            //第二步：获取连接
            //第一种方式：利用DriverManager（常用）
            //connect = DriverManager.getConnection("jdbc:oracle:thin:@localhost:1521:XE", "你的oracle数据库用户名", "用户名密码");

            //第二种方式：直接使用Driver
            Properties pro = new Properties();
            pro.put("user", "你的oracle数据库用户名");
            pro.put("password", "用户名密码");
            connect = driver.connect("jdbc:oracle:thin:@localhost:1521:XE", pro);

            //测试connect正确与否
            System.out.println(connect);  


            //第三步：获取执行sql语句对象
            //第一种方式:statement
            //statement = connect.createStatement();

            //第二种方式：PreStatement
            PreparedStatement preState = connect.prepareStatement("select  * from tb1_dept where id = ?");


            //第四步：执行sql语句
            //第一种方式：
            //resultSet = statement.executeQuery("select  * from tb1_dept");

            //第二种方式：
            preState.setInt(1, 2);//1是指sql语句中第一个？,  2是指第一个？的values值
            //resultSet = preState.executeQuery();        //执行查询语句
            //查询任何语句，如果有结果集，返回true，没有的话返回false,注意如果是插入一条数据的话，虽然是没有结果集，返回false，但是却能成功的插入一条数据
            boolean execute = preState.execute();
            System.out.println(execute);

            //第五步：处理结果集
            while (resultSet.next())
            {
                int id = resultSet.getInt("id");
                String name = resultSet.getString("name");
                String city = resultSet.getString("city");
                System.out.println(id+"   "+name+"   "+city);  //打印输出结果集
            }
        } catch (Exception e) {
            e.printStackTrace();
        }finally {
            //第六步：关闭资源
                try {
                    if (resultSet!=null) resultSet.close();
                    if (statement!=null) statement.close();
                    if (connect!=null) connect.close();
                } catch (SQLException e) {
                    e.printStackTrace();
                }
        }
    }
}

3.连接SqlServer数据库

package com.connDBTest;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;

public class GetConnectionSqlServer {
    public void getConnectionSqlServer() {

        String driverName = "com.microsoft.jdbc.sqlserver.SQLServerDriver";
        String dbURL = "jdbc:sqlserver://localhost:1433;databasename=USCSecondhandMarketDB"; // 1433是端口，"USCSecondhandMarketDB"是数据库名称
        String userName = "sa"; // 用户名
        String userPwd = "sa"; // 密码

        Connection dbConn = null;
        try {

            Class.forName(driverName).newInstance();
        } catch (Exception ex) {
            System.out.println("驱动加载失败");
            ex.printStackTrace();
        }
        try {
            dbConn = DriverManager.getConnection(dbURL, userName, userPwd);
            System.out.println("成功连接数据库！");
        } catch (Exception e) {
            e.printStackTrace();
        } finally {

            try {
                if (dbConn != null)
                    dbConn.close();
            } catch (SQLException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }
    }

    public static void main(String[] args) {
        GetConnectionSqlServer getConn = new GetConnectionSqlServer();
        getConn.getConnectionSqlServer();

    }
}